ABS examines energy-saving technology

13 Sep 2010
CFD simulation showing propeller/hull interaction (Graph courtesy of ABS)

CFD simulation showing propeller/hull interaction (Graph courtesy of ABS)

ABS and the Shanghai Merchant Ship Design & Research Institute have entered into a two-year joint research and development project to study the potential of an energy-saving device to enhance propulsion efficiency.

“We will use computational fluid dynamics (CFD) technology to analyse the flow field and will specifically look to see if the device developed by SDARI does indeed create more efficiency by equalising the wake quality and recovering certain rotation energy,” explained Sing Kwan Lee, ABS principal engineer shared technology, who is managing the class society’s participation in the project.

According to Lee, it is the expectation that the analysis will confirm a 3%-4% increase in efficiency with the use of the device placed in front of the propeller. With this expected range of efficiency and using data published in a second IMO Greenhouse Gas Study in 2009, a Capesize bulk carrier could save between 450 to 760 tons of fuel in a one-year period.

According to ABS, there are many different ways in which energy is lost, thus reducing efficiency. For example, friction resistance, wave resistance, propeller friction and propeller axial or swirl flow loss. “Wave resistance is just one part of the total resistance,” explained Lee. “Even if a large reduction of wave resistance through hull optimisation can be achieved, this will not bring significant impact to the energy-saving propulsion. The dominant resistance of a full-form ship, like a bulk carrier, is mainly due to the viscous resistance.” Therefore, the study concentrates on using CFD techniques including the Reynolds-averaged Navier-Stokes (RANS) computation to create detailed flow characteristics in order to study and assess the suitability of the design device.

“The detailed flow field obtained from CFD simulation will be essential design information for selecting the type of energy-saving device and locating it to an appropriate position,” Lee added.

Because the study will evaluate the design device based not only from a resistance standpoint but also from a more holistic propeller/hull/rudder interaction optimisation perspective, it is one of the most detailed investigations to date on the subject. The study will be conducted in two phases: phase one will focus on analysis and design while phase two will focus on model testing of the device.

SDARI is a ship design consultancy within China’s State Shipbuilding Corporation (CSSC) and has extensive experience in designing various types of ships and says that it has accumulated more than 800 as-built designs in the past four decades.

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